α,β-Unsaturated ethers are homopolymerized or copolymerized with other compounds to give synthetic resins, adhesives and lubricating oils as well as intermediates for medical agents, agrichemicals and aroma chemicals, and therefore they are important materials in the industry. The α,β-unsaturated ethers are generally produced by pyrolysis of acetals. This thermal decomposition reaction usually involves a catalyst.
Patent Document 1 discloses catalysts used in the pyrolysis reaction. The catalysts disclosed are sulfates of metals having higher ionization tendency than hydrogen, or supported catalysts in which the metal sulfates are supported on solid carriers such as alumina and silica gel. The supported catalysts specifically disclosed in the document are calcium sulfate and manganese sulfate supported on alumina or magnesium silicate. They show relatively high catalytic performance in the conversion of acetal that is a starting material. However, selectivity for α,β-unsaturated ethers is often insufficient. Further, the patent document does not address the life of the catalysts.
Patent Document 2 discloses that catalyst systems containing a specific apatite achieve high catalytic activity and selectivity and have a long catalyst life. However, the document does not deal with sufficiently the regeneration of the catalysts or conventional catalysts.
Meanwhile, it is desired that catalysts in the industrial processes do not require frequent exchange to ensure productivity. In particular, the exchange frequency is desirably less than one time a year. In the pyrolysis of acetals, the high reaction temperature causes reaction such as polymerization of α,β-unsaturated ethers produced or by-product acetaldehydes, and the catalysts are quickly decayed and should be replaced frequently. Therefore, extended catalyst life is required particularly in the thermal decomposition of acetals.    Patent Document 1: JP-B-S41-5376    Patent Document 2: WO 2007/086496